This application claims the benefit of Korean Application No. 2002-41369, filed Jul. 15, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a developing apparatus for a liquid type printer, and more particularly, to a developing apparatus for a liquid type printer which uses a developer in high concentration.
2. Background of the Related Art
Generally, image forming apparatuses such as laser printers or copiers are classified according to developing types, such as a dry type using a powder toner and a liquid type using a toner mixed in a liquid carrier. These two types develop a predetermined image by supplying a toner to a photosensitive medium such as a photoconductive drum in which an electrostatic latent image is formed. Then, a developed image is printed on paper by passing the paper in between the photoconductive drum and a transferring media rotating in connection with the photoconductive drum. Recently, the liquid developing type has been widely used.
A liquid developing apparatus using toner particles having a size below 0.5xcx9c5 xcexcm has an advantage of getting a high definition image when developing the electrostatic latent image formed on the photosensitive medium.
The liquid developing apparatus obtains an appropriate image density by lowering an ink density of a liquid developer to a lower level, for example, to below about 3%. In order to supply a sufficient amount of developer to a development area and to collect it, a complex system of supplying a developer (such as an ink delivery system) is required and as a result, a volume of a printer becomes bigger and a structure thereof becomes complicated. Also, there is a requirement for a device to control an ink density of the liquid developer required during re-supply of ink due to changes in the toner particles.
FIG. 1 is a schematic diagram of a developing apparatus in a conventional liquid type printer. Referring to FIG. 1, ink with an initial density of about 1.8xcx9c2.0% is controlled by a separate density control system (not shown) and then is supplied to a manifold 1a through a pump. The supplied ink is conveyed by a deposit bar 1 to a developing roller 2 to a certain thickness. A gap between the deposit bar 1 and the developing roller 2 is about 400 xcexcm, and the ink passing through the gap is stuck to the developing roller 2 so that the ink density is increased to about 15xcx9c7%. Over-supplied ink is removed from the developing roller 2 by a squeegee roller 3. The density of the ink on the developing roller 2 is again increased to about 20%. The ink having such high density is conveyed from the developing roller 2 to an electrostatic latent image area of a photosensitive medium 6. Residual ink on the developing roller 2 is cleaned by a cleaning roller 4, and the ink on the cleaning roller 4 is removed by a sponge roller 5.
In the developing apparatus for the liquid type printer having the above-described construction, the construction of the developing apparatus becomes complicated to obtain the ink with the high density. Furthermore, since an ink feeding system and system to regulate the ink density at the initial value as described above are required, there exists a problem that the printer has to be increased in size and therefore, becomes unsuitable for general office use.
Accordingly, it is an aspect of the present invention to provide a developing apparatus for a liquid type printer that is improved to control a wrap around.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing and/or other aspects of the present invention are achieved by providing a developing apparatus for a liquid type printer. The developing apparatus includes an ink supplying unit to supply ink having a high density, and a developing tank to receive the ink up to a predetermined level. The developing apparatus also includes a developing roller positioned to rotate in the developing tank and keep a predetermined developing gap from a photosensitive medium, and to supply the ink to the photosensitive medium. The developing apparatus includes a metering unit, rotated in the ink in the developing tank to control an amount of the ink conveyed to the developing roller and moved to the developing gap, and a cleaning roller to clean the ink remaining after the ink is conveyed from the developing roller to the photosensitive medium.
According to an aspect of the invention, the metering unit includes a metering roller positioned to rotate in the developing tank at a predetermined metering gap from the developing roller.
According to an aspect of the invention, the density of the ink received in the developing tank is 6xcx9c18%.
According to another aspect of the invention, the cleaning roller rotates in the same direction as the developing roller while being connected to the developing roller to pump up the ink in the developing tank to a portion between the developing roller and the metering unit.
According to yet another aspect of the invention, the cleaning roller includes a sponge which includes micro cells below 50 xcexcm.
According to an aspect of the invention, the developing apparatus includes an ink conveying roller positioned to rotate in the developing tank to convey the ink to a side of the cleaning roller.
According to an aspect of the invention, the cleaning roller is formed with conductive materials to receive an applied voltage from a predetermined power source.
According to an aspect of the invention, the metering unit includes a friction plate, elastically connected to the developing roller, and elastically stressed by a rotary power of the developing roller and the ink, to control an amount of the ink to be regularly supplied to the developing roller.